$ { \left[\begin{array}{rrr}{1} & {-2} & {-1} \\ {-1} & {-1} & {4}\end{array}\right]-\left[\begin{array}{rrr}{3} & {4} & {0} \\ {-1} & {1} & {2}\end{array}\right] = {?} } $
To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{rrr}{1}-{3} & {-2}-{4} & {-1}-{0} \\ {-1}-{-1} & {-1}-{1} & {4}-{2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-2} & {-6} & {-1} \\ {0} & {-2} & {2}\end{array}\right]}$